No, it's the law of averages. Quality psus have roughly a 1% failure rate. Granted with a million units that's still 10,000 psus that are bunk in one form or another. What's rated tier5 are units that have closer to a 20% failure rate. For that same million units that's 200,000 that go bunk. And going bunk, with little to no protective circuitry, that short goes directly to everything plugged into the psu. If you happen to be gaming, the gpu will take a massive hit.
Tier5 units are also often mislabeled, complete fabrications of power potential. They'll claim 700w, but only have a single 75w pcie for the 18A 12v rail, the rest of the 700w taken up by the 3.3v and 5v rails, which are next to useless since IDE disappeared.
https://youtu.be/f6snWfd1v7M
You seem to have gotten lucky so far, there's more than a few users of cheap psus that are under the impression that more power is better, so will use a 650-700w psu for a 200-300w system, so scrape by on pure luck. If they ever tried like the video to use much more than 50% of that cheap psu, the chances of failure skyrocket.
It's up to you of course to have faith in that cheap psu, but it's not something I'd ever recommend. Considering the minor difference in price between quality and cheap units vrs the price of a decent gpu, mobo, ram, drives, cpu, I'll pay the extra $40 or so. Seriously cheap insurance.